Device and method for springing a vehicle seat

ABSTRACT

The invention relates to a spring device for a vehicle seat, in particular a utility vehicle seat having at least one air spring arranged between a seat part and a lower part for the height adjustment ( 5 ) of the seat part and having a control device for controlling the supply and discharge of at least one additional air volume to or from the air spring, wherein at a predefined run in and/or run out position ( 9 ) of the air spring, the additional air volume that can be supplied or discharged can be changed or switched off by means of the control device such that inclines in the profile of a force-path air spring characteristic ( 1; 1   a   , 1   b   , 1   c ) of the air spring in a first and in at least one further range ( 2, 3, 4 ) are different from one another. Furthermore, a description is given of a method of springing a vehicle seat.

[0001] This application claims the priority benefit of GermanApplication No. DE 103 17 134.7, filed Apr. 14, 2003 and GermanApplication No. DE 103 17 122.3, filed Apr. 14, 2003, which are herebyincorporated by this reference in their entireties.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

[0002] The invention relates to a device and method for springing avehicle seat, in particular a utility vehicle seat having at least oneair spring arranged between a seat part and a lower part for the heightadjustment of a seat part and having a control device for controllingthe supply and discharge of at least one additional air volume to orfrom the air spring, according to the preambles of Patent Claims 1 and11.

[0003] Spring devices for vehicle seats are known in particular forattenuating a height excursion of the vehicle seat when travelling overuneven road surfaces, such as potholes. EP 1 188 608 A1 discloses anactive suspension system for sprung vehicle seats, in which a pneumaticoffload device and a hydraulic actuating member are arranged between aseat part and a lower part that is connected to the vehicle, along witha mechanical flexible connection device. Both the pneumatic offloaddevice and the hydraulic actuating member are controlled by a controldevice as a function of a seat error signal, which is generated forexample by a jerky height adjustment of the seat part.

[0004] Such hydraulic actuating members require a connection to theon-board power supply of the vehicle, in particular of a utilityvehicle. Such a connection results in the function of the activesuspension of the vehicle seat being dependent on the function of theon-board power supply and in particular the parameters thereof, so thatit is necessary to match the parameters of the suspension system to theparameters of the on-board power supply and thus to adapt the system tothe respective utility vehicle.

[0005] Moreover, air springs are known which have a force-path airspring characteristic that runs linearly, the incline of which can bechanged as a function of the design of the air spring and of an appliedadditional air volume, but which have the same incline over the entireforce-path air spring characteristic. In such air springs, use isgenerally made of additional air volumes that are kept constant, whichas actual air volume of the air spring are associated with the airspring moving in and out.

[0006] Such additional air volumes which are kept constant result in aswinging back of the seat part into a central position of the force-pathair spring characteristic not being possible when the air spring is setwith a force-path air spring characteristic having a small incline,since friction forces within the spring device as a whole are greaterthan a return force within the force-path air spring characteristic.

[0007] On the other hand, when the spring device is designed such thatthe return force is greater—that is to say a greater incline in the airspring characteristic is set—a comparatively hard damping is achievedboth in the middle travel region and in the end of travel regions of theair spring.

[0008] Moreover, when using an air spring in an air springcharacteristic range with a small incline—the so-called comfortrange—which requires that a large additional volume be switched on,reaching of the end stops in the end of travel regions of the air springin the event of large in and out movements becomes probable on accountof a high degree of unevenness, as a result of which there is a reducedseating comfort for the user of the vehicle seat. The setting of acomfort range is generally desired in the case of air springs forvehicle seats on account of better transmission values and the higherdegree of comfort resulting therefrom.

SUMMARY OF THE INVENTION

[0009] Accordingly, it is an object of the present invention to providea spring device for a vehicle seat, which spring device can operate andalso be installed and removed independently of a hydraulic or pneumaticon-board power supply and provides a high degree of travelling comfortfor a user when using the vehicle seat in a comfort range which isreproduced by a force-path air spring characteristic having a very smallincline. Furthermore, it is an object of the invention to provide amethod of springing a vehicle seat using such a spring device.

[0010] This object is achieved in respect of the device by the featuresof Patent claim 1 and in respect of the method by the features of Patentclaim 11.

[0011] An essential point of the invention is that in a spring devicefor a vehicle seat having at least one air spring arranged between aseat part and a lower part for the height adjustment of the seat partand having a control device for controlling the supply and discharge ofat least one additional air volume to or from the air spring, theadditional air volume that can be supplied or discharged can be changedor switched off by means of the control device at a selectable run inand/or run out position of the air spring such that an incline in theprofile of a force-path air spring characteristic of the air spring in afirst and in at least one further range are different from one another.By way of example, an increase in the incline of the force-path airspring characteristic for the further ranges has the effect, in end oftravel regions of the air spring, that when using an air springcharacteristic with a small incline in the first range, firstly, uponreaching the predefinable in or out position of the air spring, a returnforce is obtained that is sufficient to bring about a return of the seatpart into the central position of the flat air spring characteristicwithin the first range. Secondly, the end stops of the air spring maynot be reached since there is a sufficient spring force on account ofthe steeper air spring characteristic in the further range.

[0012] The additional air volume that can be supplied or discharged inthe at least one further range which follows the first range is smallerthan in the first range or completely zero and may be supplied ordischarged in a number of stages, preferably in three stages. In thisway, different degrees of damping can be set as a function of thedesired seating comfort.

[0013] Such vehicle seats are preferably used for utility vehicles suchas tractors, construction site vehicles and stacking trucks and in thefirst range with a flat characteristic have an additional air volume ofmore than 0.11 at a natural seat frequency of for example around 1.0 Hzand a transmission value from a range of 0.1-0.9. The additional volumein the first range is greater than 0.11. The additional volume in thefurther range is either 0.01 or greater than 0.01. Preferably, theadditional volume in at least one further range is smaller than in thefirst range. As a result, when the in position of the air spring isexceeded, there is an increase in the spring force which allows the airspring to come out quickly and returns the user of the vehicle seat oncemore to the central position within the first range of thecharacteristic.

[0014] Likewise, when a defined out position is exceeded, there is aloss of spring force within the air spring which brings the air springquickly back in and accordingly makes the user fall back into thepredefined central position of the characteristic within the firstrange.

[0015] According to one preferred embodiment, the spring device has anadjustment device for the automatic height adjustment of the seat partat the start of a use operation by a user having a predefined weight,with air being supplied to or discharged from the air spring such thatthe air spring can adjust to a central position in the first range ofthe force-path air spring characteristic. The adjustment devicecomprises, in the region of the armrest of the vehicle seat, a regulatorswitch for operating the adjustment device. Automatic positioning of theuser in the comfort range of the spring device, namely at the centralposition in the first range of the characteristic, as a function of hisweight is thus possible, without thereby reducing the further range inwhich the characteristic has a greater or smaller incline.

[0016] According to one preferred embodiment, the spring device has arecognition device for recognizing a user using the vehicle seat, inparticular by means of his weight, in order to allow the automaticactivation of the height adjustment when the user sits down in thevehicle seat.

[0017] The first range of the force-path air spring characteristicpreferably corresponds to a length of travel of the air spring of up to3000 mm, whereas the at least one further range corresponds to a lengthof travel of preferably up to 2000 mm.

[0018] The at least one further range adjoins the first range on theleft-hand or right-hand side as of the defined run in and/or run outpositions of the air spring.

[0019] The exceeding of the run in and run out positions is recognizedby means of recognition and switching devices and the spring device isswitched to supply and discharge the changeable additional air volume bymeans of the control device. An automatic transition of the springcharacteristic from a comfort range (first range) into a progressionrange (further range) and/or a degression range (further range) is thusensured.

[0020] In a method of springing a vehicle seat, according to theinvention, when the air spring exceeds the selectable run in and/or runout positions, the additional air volume that can be supplied ordischarged is changed or switched off by means of the control device inorder to change the incline in the profile of the force-path air springcharacteristic in the first and in at least one further range. In theevent of the run in and run out positions being exceeded, the changeableadditional air volume is supplied or discharged only when recognitionand switching devices in first and second end of travel regions areactivated on account of vibration, regularly and at a high frequency bythe air spring moving in and out. The consequence of this is that in theevent of the air spring moving in and out in an irregular manner or inthe event of the in and out movement taking place with long timeintervals (smaller than or equal to 1.0 Hz), uneconomical activation ofthe recognition and switching devices is avoided, thereby achieving anenergy saving.

[0021] Further preferred embodiments are given in the dependent claims.

DESCRIPTION OF THE DRAWINGS

[0022] Advantages and expedient features of the invention can be foundin the following description in conjunction with the drawing, in which:FIG. 1 shows a schematic diagram of a force-path air springcharacteristic of a spring device according to one embodiment of theinvention; FIG. 2 shows a schematic diagram of the air springcharacteristic shown in FIG. 1, in a displaced position, and FIG. 3shows a schematic diagram of the air spring characteristic shown in FIG.1, in a further displaced position.

DETAILED DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 shows a schematic diagram of the profile of a force-pathair spring characteristic 1 according to one embodiment of theinvention, where the air spring characteristic 1 is made up of thesections 1 a, 1 b, 1 c. In the diagram, the turn path s of the airspring is plotted on the abscissa.

[0024] Ideally, the individual sections 1 a, 1 b and 1 c run so thatthey merge fluidly into one another such that the transitions may bearc-shaped, with it being possible for the arcs to have differentdimensions.

[0025] In a first comfort range 2, in which an additional air volume ofmore than 0.1 litre is supplied to or discharged from the air spring,the air spring characteristic has the section 1 awith a small incline.In a second progression range 3, in which an additional air volume thatis smaller than the additional air volume discharged in the firstcomfort range 2 is supplied, the air spring characteristic 1 has thesection 1 b with a greater incline than that in section 1 a. Likewise,in a third degression range 4, in which an additional air volume that isalso smaller than the additional volume discharged in the first comfortrange 2 is discharged, the air spring characteristic has thecharacteristic section 1 c with a greater incline than in section 1 a.

[0026] A height adjustment 5 in the event of the air spring moving inand out as a result of vibration, as occurs for example when travellingover potholes in the road, is carried out within the first, second andthird ranges 2, 3, 4. The ranges 2, 3 and 4 are combined in a switchingwindow 6.

[0027] Within the first comfort range 2, a seat part of the vehicle seatis ideally arranged in a central position 7 of the characteristic, withit being possible for the central position 7 to be displaced verticallyon an HA line 13 as ideal line.

[0028] As soon as a departure is made from the first comfort range 2 onthe left-hand or right-hand side on account of the spring element movingin or out and a predefined run in or run out position 8, 9 is exceeded,a recognition and switching device 8 a, 9 a recognizes this and switchesthe entire spring device to supply or discharge the other additional airvolume, specifically having a smaller volume.

[0029] The comfort range 2 corresponds to a length of travel 10 theupper limit of which may lie within a range of 0.1-3000 mm depending onthe technical requirements, whereas the digression range 4 and theprogression range 3 may have lengths of travel 11, 12 with upper limitsof 0.1-2000 mm.

[0030] The sequence of operation of the spring device according to theinvention is as follows:

[0031] 1. A driver takes up his position in the vehicle seat and arecognition by virtue of his weight is carried out by means of a driverrecognition device. The weight loading of the spring device leads to anexceeding of the predefined run out position 9.

[0032] By means of an air supply (not shown here), air is automaticallylet into the spring device, whereupon the driver is guided with the seatpart into the central position 7 within the comfort range.

[0033] The central position 7 may be displaced within the force-pathdiagram in order to set a desired individual height of the seat part byusing an operating device, which is preferably fitted in the armrestregion of the vehicle seat, to displace the switching window 6 withinthe diagram, as shown for example in FIGS. 2 and 3. FIGS. 2 and 3 showthe position of the switching window with the associated first, secondand third ranges 2, 3, 4 in the case of a seat part that has beenheight-adjusted in the upward and downward direction, respectively.

[0034] 2. As soon as a regularly high frequency vibration (≧1.0 Hz,pulse number of 10) occurs and this is recognized by the recognition andswitching device, upon activation of the recognition and switchingdevice 9 a a signal is output to the air supply, by means of a controldevice (not shown here), to raise the HA position 7. In the event of anirregular vibration with long time intervals (≦1.0 Hz), no signal isoutput.

[0035] 3. Upon repeated, regularly high frequency contacting of therecognition and switching device 8 a (≧1 Hz, pulse number of 10), asignal is output to the air supply, by means of the control device, tolower the HA position 7 by discharging air. In the event of an irregularvibration with long time intervals (≦1.0 Hz), no such signal is output.

[0036] 4. The control device calculates, at defined time intervals, suchas for example in the order of magnitude of 1.0 s, the mean value of thevibration amplitudes and brings the profile thereof into congruence withthe selected HA line 13 by supplying or discharging compressed air.

[0037] 5. The HA line 13 lies in the centre of the comfort window, thewidth of which can be regulated in a stepped or stepless manner by wayof rotary switches or step switches. The width of the comfort windowcorresponds to a length of travel the upper limit of which lies in arange of 0.1-3000 mm.

[0038] The progression range 3 starts from the position 9 and becomes asteep characteristic with an additional air volume of for example 0.01or a value greater than 0.01. The spring device thereby becomes rigid inthe lower range, i.e. including outside the comfort range, as a resultof which a deflection or an end stop of the air spring is reduced. Theminimum value of the length of travel is required for this. A return ofthe air spring in the direction of the HA position 7 then takes place.

[0039] 6. If, in the event of permanently strong vibration excitation, acharacteristic in the progression range having an incline whichcorresponds to an additional air volume of greater than 0.01 is notsufficient, an even steeper characteristic, which corresponds to anadditional air volume of 0.01, is used. Should this characteristic alsonot suffice for sufficient damping, the complete switching window isautomatically displaced upwards in steps, as shown by the arrow 14 inFIG. 2.

[0040] 7. Similarly, in the degression range, in the event of aninsufficiently great incline in the characteristic, which corresponds toan additional air volume of more than 0.01, an additional air volume of0.01 is used. Should such a characteristic also not allow the necessaryloss of force in the degression range for the rapid lowering of thedriver and of the vehicle seat, then the complete switching window 6 isautomatically displaced downwards in steps, as shown by the arrow 15 inFIG. 3.

[0041] The control device advantageously comprises software which ismatched to the respective vehicle type and to the character thereof,with it being possible for the software to be optimized in animprovement process that is carried out continuously. By reading via aPC or via a laptop, the vehicle occupant receives a current updateversion of the software.

[0042] Preferably, by changing the basic software it is possible tochange the use purpose of the vehicle seat such that, for example, a useof the vehicle seat both in a large tractor with a sprung cabin and in asmall tractor is possible.

[0043] All the features of the invention are considered essential to theinvention both individually and in combination. Modifications thereofare familiar to the person skilled in the art.

1. Spring device for a vehicle seat, in particular a utility vehicleseat having at least one air spring arranged between a seat part and alower part for the height adjustment (5) of the seat part and having acontrol device for controlling the supply and discharge of at least oneadditional air volume to or from the air spring, characterized in thatat a selectable run in and/or run out position (8, 9) of the air spring,the additional air volume that can be supplied or discharged can bechanged or switched off by means of the control device such thatinclines in the profile of a force-path air spring characteristic (1; 1a, 1 b, 1 c) of the air spring in a first and in at least one furtherrange (2, 3, 4) are different from one another.
 2. Spring deviceaccording to claim 1, characterized in that in the range (3, 4) of theforce-path air spring characteristic (1; 1 a, 1 b, 1 c) thevibration-damping additional air volume that can be supplied ordischarged is greater or smaller than in the first range (2) or iscompletely switched off.
 3. Spring device according to claim 1,characterized in that the additional air volume in the further range (3,4) can be supplied to or discharged from the air spring in each case ina number of stages, preferably in three stages.
 4. Spring deviceaccording to claim 1, characterized by at least one pneumaticdirectional control, valve for supplying/discharging the additional airvolume(s).
 5. Spring device according to claim 1, characterized by anadjustment device for the automatic height adjustment of the seat partat the start of a use operation by a user having a predefined weight bymeans of air being supplied to or discharged from the air spring suchthat the air spring adjusts to a central position (7) in the first range(2) of the force-path air spring characteristic (1; 1 a, 1 b, 1 c). 6.Spring device according to claim 5, characterized in that the firstadjustment device comprises a regulator switch that is arranged in theregion of the armrest of the vehicle seat.
 7. Spring device according toclaim 1, characterized in that the first range (2) within the force-pathair spring characteristic (1; 1 a, 1 b, 1 c) can be displaced by meansof an operating device by the user and by means of the control devicesuch that the seat part is adjusted to the desired height.
 8. Springdevice according to claim 1, characterized by a recognition device forrecognizing a user using the vehicle seat, in particular by means of hisweight.
 9. Spring device according to claim 1, characterized in that theadditional air volume that can be supplied and discharged is greaterthan 0.11 in the first range (2) of the force-path air springcharacteristic (1; 1 a, 1 b, 1 c) and is either 0.01 or greater than0.01 in the further range.
 10. Spring device according to claim 1,characterized by recognition and switching devices (8 a, 9 a) forrecognizing the selectable run in and run out positions (8, 9) of theair spring and for switching the spring device to supply and dischargethe changeable additional air volume by means of the control device. 11.Method of springing a vehicle seat, in particular a utility vehicle seathaving at least one air spring arranged between a seat part and a lowerpart for the height adjustment (5) of the seat part and having a controldevice for controlling the supply and discharge of at least oneadditional air volume to or from the air spring, characterized in thatwhen the air spring exceeds a predefinable run in and/or run outposition (8, 9), the additional air volume that can be supplied ordischarged is changed or switched off by means of the control device inorder to change in a further range (3, 4) an incline in the profile of aforce-path spring characteristic (1; 1 a, 1 b, 1 c) with respect to afirst range (2).
 12. Method according to claim 11, characterized in thatthe exceeding of the predefined run in and run out position (8, 9) ofthe air spring is recognized by means of recognition and switchingdevices (8 a, 9 a) and the spring device is switched by means of thecontrol device to the changeable additional air volume for the furtherrange (3, 4).
 13. Method according to claim 12, characterized in that inthe event of switching of the spring device, the changeable additionalair volume is supplied to the air spring only when the recognition andswitching devices (8 a) in a first end of travel region are activated onaccount of vibration, regularly and at a high frequency by the airspring moving in and out.
 14. Method according to claim 12,characterized in that in the event of switching of the spring device,the changeable additional air volume is discharged from the air springonly when the recognition and switching devices (9 a) in a second end oftravel region are activated on account of vibration, regularly and at ahigh frequency by the air spring moving in and out.
 15. Method accordingto claim 11, characterized in that in the event of insufficientvibration damping in the end of travel regions of the air spring withrespect to a residual travel path, the changeable additional air volumeis reduced towards one end of travel until a sufficient damping of theair spring is achieved without touching of the end of travel by an airspring lifting cylinder.